While some Martian meteorites contain minor abundances of clays formed on Mars, most of our understanding of the clay mineralogy of Mars comes from orbital infrared remote sensing measurements. The European Space Agency’s Mars Express spacecraft was, in 2004, the first mission to detect clay minerals on Mars. Since that time, both Mars Express and NASA’s Mars Reconnaissance Orbiter have detected >10,000 deposits spanning a range of geologic contexts and mineralogies. These deposits are extremely interesting for many reasons, not the least of which is that they seemingly date to an era not preserved on Earth (>3.7 Ga).

In this talk, Joe will describe an updated perspective on the mineralogy of Martian clays, and their implications for ancient aqueous geological processes on and habitability of Mars.

Javier Cuadros, Department of Earth Sciences, Natural History Museum, London

Confinement appears to be essential at the mineral-microbial interface and has an effect on both, microbial development and mineral formation. The role of confinement starts before life itself. Prebiotic molecules had to be concentrated from water or gas and "confined", possibly within clay interlayers, where they could react, be protected from adverse physical and chemical conditions, and perhaps also where specific reactions were catalysed.

Microorganisms frequently confine themselves within organic or inorganic walls for a number of reasons such as protection and feeding. They build exopolysaccharide capsules, burrow into mineral grains, etc. Close contact or confinement within mineral grains is arguably the habitat of the largest portion of existing microorganisms.

Microbial confinement has a feed-back effect on minerals. Microbes burrowing into mineral grains contribute to mineral weathering. Confined spaces inhabited by microorganisms, such as burrows, biofilms, exoskeletons of dead microbial algae, have chemical conditions different from the surrounding environment and impact mineral crystallization. For example, glauconite originates largely in connection to biological decay within marine shells. Microbial activity can thus control to some extent the chemistry, mineralogy and formation rate of the neoformed phases. Clay minerals are obviously affected by microbially-mediated confinement of mineral-solution systems, as they are typically formed in the range of conditions in which these processes take place.

What was the role of water on Mars in the past? Much of what we know about Mars has been from observation from a distance. Although a few missions have landed scientific equipment on the surface, and some meteorites from Mars have landed on the Earth's surface, a huge amount of data have been gathered from orbiting missions and from other remote observation techniques. The geology of the surface can be studied by looking at infrared and other radiation: different minerals react differently to particular sorts of light and radiation.

Javier Cuadros, a clay specialist in the Museum's Mineralogy Department, has been successful in being awarded money from the EU to host a research fellow under the Marie Curie scheme to explore the origin of Iron/Magnesium-rich clay minerals on Mars.

Clays have been discovered on Mars in the past five years using near-infrared spectroscopy - this is of particular importance because the presence of clay shows for the first time unambiguous evidence for long-term water activity on Mars. Understanding the conditions of formation of theseFe/Mg-rich clays is central to revealing Mars' climate history; and the possiblity of there having been conditions suitable for life in the past .

The study will focus on marine systems on Earth that produce abundant Mg- and Fe-rich clays (talc, saponite and nontronite). These clays are often intimately mixed by chemical and physical processes and seem similar to Martian clays. It seems possible that similar water conditions on Mars may have generated the Fe/Mg-clays. The Earth clays from several submarine hydrothermal fields will be studied using advanced microscopy, chemical, spectroscopic, structural and isotope analytical techniques to fully characterise their crystal-chemistry and to define the environment in which they formed (temperature, fluids, mineral assemblages).

These infrared and other data for Earth clay will be compared with the data from Mars and similarities and differences will give much better understanding of the past role of water on Mars.